Manually operated lens cribber

ABSTRACT

A manually operated lens cribber has a cutting compartment on a base. The cutting compartment has a door that is moveable between a closed position and an open position. A cutting tool is inside the cutting compartment and rotates about a first axis. A lens blank carrier is attached to the base in a manner to be manually movable across the base on a second axis that is substantially perpendicular to the first axis. The lens blank carrier has a hand operated screw mechanism on which a lens blank can be mounted and which moves the lens along a third axis that is substantially parallel to the first axis. A releasable end stop is positioned on the base for positioning the lens blank carrier relative to the cutting tool so that the desired amount of material is removed from the lens blank. A calibration and positioning scale is also provided.

FIELD OF INVENTION

The invention relates to apparatus which are used to reduce the diameter of a lens blank. This type of device is often called a cribber.

BACKGROUND OF THE INVENTION

Lenses for eyeglasses and optical devices are usually made from plastic lens blanks that are cylindrical and have a diameter that is larger than the diameter of the finished lens. The process that is typically used to make a finished plastic lens from a lens blank begins by cutting the lens blank so that the lens blank that has a smaller diameter which is closer in diameter to the desired diameter of the finished lens. This process of removing excess materials from a lens blank is called cribbing regardless of the device used to remove that excess material. After the lens blank has been cribbed the lens is cut to the shape required by the prescription and then polished. Later in the process the lens will be cut to fit the eyeglass frame. The process of making a finished lens from a lens blank originally was a manual operation using hand tools to cut or grind and polish the lens blank to create the desired lens. That process was slow, tedious and did not eliminate breakage. Consequently, the art developed a variety of machines to automate the lens making process.

U.S. Pat. No. 3,568,370 to Wicksall discloses a lens cribber in which a lens blank is held near one end of a lens carrier. The opposite end of the lens carrier is pivotably attached to a housing that contains a grinding wheel. The lens block holding the lens blank is on a spindle which is driven by a belt. The lens carrier is lowered to position the lens blank against the grinding wheel. The object of this invention is to provide a machine which will effect cribbing of lens blank automatically.

U.S. Pat. No. 3,449,866 discloses an automatic cribbing device in which an air cylinder is used to move the lens blank to and away from a grinding wheel.

U.S. Pat. No. 4,561,213 to Tusinski et al. discloses an apparatus for polishing the edges of lenses. The lens is held in a lens holder which is rotated by motor. A hand screw mechanism is provided for opening and closing a jaw that holds the lens. A polishing pad is located above the lens holder. A hand mechanism is provided for moving the polishing pad left and right so that different sections of the polishing pad will contact the lens. A handle is provided for moving the polishing pad toward and away from the lens.

U.S. Pat. No. 5,485,771 to Brennan et al. discloses an apparatus for generating ophthalmic products from blanks. One embodiment is shown in FIG. 1 and a second embodiment is shown in FIG. 3. In both embodiments a lens blank (not shown) is held in a chuck which is turned by a motor. A cutting tool is provided to cut the lens blank. In the embodiment of FIG. 1 the cutting tool can be moved along the x-axis by a motor on a slide and can be moved along the y-axis by a second motor on a second slide. In the embodiment of FIG. 3 the cutting tool can be moved along the x-axis and the lens blank can be moved along the y-axis. A computer is provided in both embodiments to control the movement of the lens blank and the cutting tool.

U.S. Pat. No. 7,975,356 B2 to Schafer et al. discloses a machine for processing optical work pieces. This computer controlled machine has an adjusting mechanism with a linear drive unit and a swivel drive unit that are stacked on each other.

As the art has evolved the machines used for lens cribbing have become more complicated. These machines can precisely cut a lens blank to within very close tolerances. Indeed, many machines now perform not only cribbing of the lens blank, but also cut the surfaces of the lens blank to create a prescription lens. Because they can cut within very close tolerances the machines have become more expensive to purchase as well as to operate. Furthermore, the time required to calibrate these machines is significant.

To make the machines that make prescription lens from lens blanks more cost effective, efforts have been made to increase the number of lenses that these machines can produce per hour of operation. Those efforts have focused on the design and construction of the machines rather than other factors that can increase production.

SUMMARY OF THE INVENTION

We recognized that if the lens blank had a diameter that was closer to the diameter of the finished lens than is the diameter of a standard lens blank, then a machine could produce more finished lenses per hour because less material would need to be removed. Furthermore, the cutting tools could be used to make more lenses before requiring replacement. But a machine which reduced the diameter of a lens blank before the lens blank is placed in a machine for prescription cutting would only be commercially viable if that machine were relatively inexpensive to make and to operate and could cut quickly.

We provide a manually operated lens cribber which has a cutting compartment on a base. The cutting compartment has a top, side walls and a door attached to the side walls. The door is moveable between a closed position and an open position such that the base, top, sidewalls and door in the closed position define an enclosed cutting chamber. A window may be provided in the top or a sidewall and a light can be provided inside the cutting chamber. We provide a cutting device, such as a router, which has a cutting tool that is within the cutting chamber and rotates about a first axis. We further provide a lens blank carrier attached to the base in a manner to be manually movable across the base on a second axis that is substantially perpendicular to the first axis. The lens blank carrier has a hand operated screw mechanism on which a lens blank can be mounted and which moves the lens blank along a third axis that is substantially parallel to the first axis. Movement of the lens blank carrier in one direction along the second axis will move at least one portion of the lens blank carrier into the cutting chamber. Movement of the lens blank carrier in an opposite direction along the second axis will move that portion of the lens blank carrier out of the cutting chamber. A releasable end stop is positioned on the base to limit the movement of the lens blank carrier so that the lens blank will be positioned adjacent to the cutting tool. We prefer to provide a scale on the base which enables the operator to precisely position the end stop for the removal of the desired amount of material from the lens blank. When the lens blank carrier abuts the end stop the lens blank will be positioned so that only a desired amount of material is removed when the lens blank is advanced and cut by the cutting tool.

We also prefer to provide a retractable pin which is moveable between a first position in which the retractable pin engages the threads of the screw mechanism and a second position in which the retractable pin does not engage the threads of the screw mechanism. Retracting the pin enables the user to rapidly pull the lens blank away from the cutting tool.

Other objects and advantages will become apparent from the description of certain present preferred embodiments of our manually operated lens cribber which is shown in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of a present preferred embodiment of our manually operated lens cribber with the cutting compartment door in a closed position.

FIG. 2 is a front perspective view similar to FIG. 1 showing the cutting compartment door in an open position.

FIG. 3 is a rear perspective view of the embodiment shown in FIG. 1.

FIG. 4 is a top view of the embodiment shown in FIG. 1.

FIG. 5 is a sectional view taken along the line V-V in FIG. 4.

FIG. 6 is a sectional view taken along the line VI-VI in FIG. 4.

FIG. 7 is a sectional view taken along the line VII-VII in FIG. 5.

FIG. 8 is an enlarged view of the scale within the circle VIII in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 through 4 and 6, a present preferred embodiment of our manual operated lens cribber 1 has a cutting compartment 2 on a base 6 which together create a cutting chamber. The cutting compartment 2 is formed by sidewalls 3, door 4 and top 5. A window 7 may be provided in the top. Legs 15 are provided on the base 6. We also prefer to provide an LED light 8 in inside the cutting chamber. The door 4 can move between a closed position shown in FIG. 1 and an open position shown in FIG. 2.

A router 10 is mounted on the base and has a cutting tool 12, shown in broken line in FIG. 4, which is located inside the cutting chamber. A standard Bosch router will work well in our device. Any router with reasonable power can be used. The higher the power the faster the user will be able to cut. The router mounting can be altered to accommodate routers from different manufacturers. The cutting tool preferably is a ball mill. We prefer to use a 20 mm diameter tungsten carbide ball mill with a ⅜ inch shank and six flutes. But many other tools can be used. For example, a diamond tool with four flutes can be used for longer cutting life.

A lens blank carrier 20 is attached to the base 6 and holds a lens blank 30. The lens blank is held by a lens block 21 which is attached to one end of a threaded rod 22 that moves within housing 18. A handle 23 is provided at the opposite end of the threaded rod. Turning the handle 23 causes the lens block and lens blank to move along a first axis A-A. As can be seen in FIG. 4 that axis A-A is parallel to a second axis B-B running through the cutting tool 12.

The lens blank carrier has a carriage 24 which rides on a rail 25. The rail has a centerline or axis which is substantially perpendicular to axes A-A and B-B. The carriage 24 allows the lens blank carrier to move the lens blank into and out of chamber within cutting compartment 2. Movement of the carriage in one direction along the second axis will move a portion of the lens blank carrier into the cutting chamber and movement of the carriage in an opposite direction along the rail will move that portion of the lens blank carrier out of the cutting chamber. There is an end stop 32 on the base which can be moved along the rail to a desired position and be locked in place by lever 34. A scale 36 is provided on the base 6 to indicate the position of the end stop relative to the cutting tool.

As can be seen most clearly in FIG. 8 the scale 36 has a fixed base 33 which has a series of marks between the numbers 22 and 9. The marks are used to calibrate the scale to match the diameter of the cutting tool which is being used. There is also a moveable slide 35 which is secured to the fixed base 33 by screws 37 that pass through slots 38. The end of the moveable slide is positioned adjacent the mark on the fixed slide that corresponds to the diameter of the cutting tool. Then the screws 37 are tightened to prevent the moveable slide form moving. The moveable slide shown in FIG. 8 is positioned for a cutting tool that is 22 millimeters in diameter. There is a second set of markings which are on the movable slide and correspond to the desired diameter of the cribbed lens blank. On the scale shown in FIG. 8 those markings correspond to diameters between 60 and 82 millimeters. There is an index line 39 on the end stop 32. The end stop is positioned so that the index line 39 will be adjacent the mark on the movable slide 35 that corresponds to the desired diameter of the cribbed lens. Then the end stop is secured in place by lever 34.

As can be seen most clearly in FIGS. 5 and 7 we prefer to provide a retractable pin 40 which engages the threads of the threaded rod 22 when the pin is in an extended position shown in FIG. 7. Then the head 41 of the pin 40 engages the threaded rod and is in the groove between adjacent threads. The head of the pin allows the threaded rod 22 to turn clockwise or counterclockwise and prevents the threaded shaft from being pushed into or pulled away from the cutting tool. When the pin 40 is retracted the threaded rod can be easily pushed toward or away from the cutting tool. This allows the user to quickly pull the lens blank away from the cutting tool after the lens blank has been cut to the desired diameter. We prefer to provide a handle 44 for retracting and engaging the pin 40. We also prefer to provide a compression spring 46 which biases the retractable pin 40 toward an engaged position. An exhaust pipe 28 extends from the cutting chamber for removing dust and other particles that are created during the lens cribbing process. This exhaust pipe should be connected to a vacuum system (not shown) when the lens blank is being cribbed.

To operate the lens cribber, an operator moves the lens blank carrier to the position shown in FIG. 2 and attaches a lens blank 30 to the lens block 21. Before or after attaching the lens blank to the lens block the operator positions the end stop for cutting the lens blank to the desired diameter. Next the operator slides the carriage of the lens blank carrier along the rail until the carrier abuts the end stop. Then the lens blank 30 will be inside the cutting compartment 2 and located opposite the cutting tool 12. The cutting tool 12 will not touch the lens blank 30. At that point the door 4 is closed and the lens blank carrier 20 is in the position shown in FIGS. 1 and 3. The router 10 is turned on causing the cutting tool 12 to rotate. Next the operator turns the handle 23 to rotate the threaded rod 22 thereby advancing the lens blank toward the spinning cutting tool. As the handle continues to be turned the cutting tool engages the face of the lens blank adjacent the edge of the lens blank. The operator continues to turn the handle until the cutting tool has passed through and removed all of the excess material that had to be removed to produce the cribbed lens blank of the desired diameter. Then the operator can pull lever 44 to retract the retractable pin 40 away from the threaded rod. That will enable the operator to quickly move the cribbed lens blank away from the cutting tool. Then operator may shut off the router, open the door and slide the lens blank out of the cutting chamber. Finally the cribbed lens blank is removed from the lens holder for further processing to create a finished lens.

The cribbed lens blank can then be put in the machine that does the cutting, grinding and polishing to make the finished lens. This machine will be able to make that finished lens from the cribbed lens blank much faster than it could have made the finished lens from a standard size lens blank with less wear on the cutting and grinding tools in that machine.

Our lens cribber is designed for use in cutting plastic lens blanks, particularly those having a diameter larger than 65 mm. It should be apparent from the drawings to those skilled in the art that our manually operated lens cribber is relatively inexpensive to build and maintain. Because this cribber has no motors other than in the router and no computer controls there are fewer components that can fail. Furthermore, because the lens cribber is manually operated any technician should be able to operate the device after only a brief training. Hence, the cost to operate the device should be relatively small. Moreover, our lens cribber is portable and can be used on a work bench or work table at any location. When not in use our lens cribber can easily be removed from the workbench and put in storage. With the preferred embodiment of a high powered router the lens blank may be reduced in size in less than 10 seconds.

While we have shown and described certain present preferred embodiments of our manual lens cribber, it should be distinctly understood that our invention is not so limited and may be variously embodied within the scope of the following claims. 

We claim:
 1. A manually operated lens cribber comprising: a base; a cutting compartment on the base, the cutting compartment having a top, side walls and a door attached to the side walls, the door being moveable between a closed position and an open position such that the base, top, sidewalls and door in the closed position define an enclosed cutting chamber; a cutting device connected to the base and having a cutting tool which is within the cutting chamber and rotates about a first axis; a lens blank carrier attached to the base in a manner to be manually movable across the base on a second axis that is substantially perpendicular to the first axis, the lens blank carrier having a hand operated screw mechanism on which a lens blank can be mounted, the hand operated screw mechanism having a handle which when turned causes the lens blank to move along a third axis that is substantially parallel to the first axis and wherein movement of the lens blank carrier in one direction along the second axis will move at least one portion of the lens blank carrier into the cutting chamber and movement of the lens blank carrier in an opposite direction along the second axis will move the at least one portion of the lens blank carrier out of the cutting chamber; and a releasable end stop on the base which is positioned on the first second axis at a location where the lens blank carrier can abut the end stop when moved along the second axis toward the end stop.
 2. The manually operated lens cribber of claim 1 also comprising a window in the top.
 3. The manually operated lens cribber of claim 1 wherein the screw mechanism has a rod with threads and a housing that surrounds at least a portion of the rod with threads also comprising a retractable pin connected to the housing and positioned to engage the rod with threads, the retractable pin being moveable between a first position in which the retractable pin engages the threads and a second position in which the retractable pin does not engage the threads.
 4. The manually operated lens cribber of claim 3 also comprising a spring attached to the retractable pin and the housing which biases the retractable pin toward the first position.
 5. The manually operated lens cribber of claim 1 also comprising an exhaust pipe which extends from the cutting chamber and is attached to the base.
 6. The manually operated lens cribber of claim 1 also comprising: a rail attached to the base and positioned on the second axis; and a carriage on the rail and attached to the lens blank carrier.
 7. The manually operated lens cribber of claim 1 wherein the end stop has an index line and further comprising a scale on the base and positioned to be adjacent the index line when the end stop is in a selected location.
 8. The manually operated lens cribber of claim 7 wherein the scale has fixed scale base which has a series of markings that correspond to diameters of cutting tools, and a moveable scale base having markings that correspond to diameters of cribbed lens blocks, at least one set screw connected between the scale base and the scale moveable base for securing the moveable base against movement relative to the fixed scale base. 